This invention relates to antennas and more particularly to a stripline slot antenna element suitable to be used in flat plate antenna arrays.
Stripline slot antennas are well known in the art. These antennas are generally formed by etching a radiating aperture (slot) on one ground plane of a stripline sandwich circuit. The stripline sandwich comprises a conducting strip, and a transmission line insulatively disposed between two ground planes. Energy is coupled to the slot over the transmission line with the electric fields propagated thereon confined within the dielectric boundaries between the ground planes. To maintain mode purity, to prevent moding problems, prior art stripline antennas have required the use of cavities formed opposite of the radiating aperture. These cavities are usually formed by either placing plated through holes at predetermined distances about the radiating aperture, or by using rivets between the ground planes. Another method is to form a physical cavity on the ground plane opposite the radiating slot.
The use of cavities has limited the bandwidth performance of these prior art antennas. Typically, the bandwidth of such stripline antennas are 3% to 5%. Hence, flat plate antenna arrays comprised of such antenna elements are typically limited to bandwidths of 2% to 3% and an efficiency factor of no greater than 35%.
Because the slot is itself a relatively broadband radiator, if the cavity could be eliminated, the bandwidth performance of a slot antenna element could be improved. Such an improvement would give rise to an associated increase in an array efficiency factor.
Thus, a need exists for eliminating a requirement for cavity backed slots in order to provide stripline slot antennas having improved bandwidth performances.
Accordingly, it is an object of the present invention to provide an improved slot antenna element.
It is another object of the present invention to provide a stripline slot antenna which requires no resonant cavity.
It is a further object of the invention to provide a stripline slot antenna of a particular configuration requiring no cavity and which is suitable to be utilized in flat plate antenna arrays.